Stackable seating units

ABSTRACT

A compactly stacking chair with a spring-resilient seat. The chair has a frame constructed to enable compact stacking. It also has a seat assembly and a back assembly, each having a series of arcuate, continuous, sinuous wires, each wire closely approaching each of its immediately adjacent wires at frequent intervals, and a thin sleevelike plastic coating surrounding the wires, following their sinuosity and joining the wires together where they closely approach each other. The approaches are close enough for effective bridging between them by the coating, and the wires and plastic coating comprise a unitary assembly defining a cylindrical arc. The seat and back assemblies are each secured to rigid frame portions across a space that flattens their arcs to flatter arcs and places these assemblies in tension along their flatter cylindrical arcs, the seat arc being convex upwardly, and the back arc being convex rearwardly. When a plurality of these chairs is stacked, each seat nests over the seat of the chair below, and the backs nest too with part of the lower surface of each seat lying within the chord across the seat of the chair above and part of the forward surface of each back lying within the chord across the back of the chair below.

iinited States Patent 11 1 Rowland Nov. 5, 1974 STACKABLE SEATING UNITS[57] ABSTRACT [76] Inventor: David L. Rowland, 8 E. 62nd St., Acompactly stacking chair with a spring-resilient seat. New York, N.Y.10021 The chair has a frame constructed to enable compact [22] Filed:Sept. 7, 1973 itlacking. It also has a seat assembly and a back assemy,each havmg a series of arcuate, contmuous, sinuppl- -I 395,266 ouswires, each wire closely approaching each of its Related US ApplicationData immediately adjacent wires at frequent intervals, and a thmsleevehke plastic coatmg surrounding the wires, [60] F' W FF 268'8701July 31 following their sinuosity and joining the wires together of 9 3March where they closely approach each other. The apat. No. 3,720,568,Contmuatron-m-part of Ser. No. 268,907, July 3, 1972, which is adivision of Proaches are close 9 for 'l brdgmg Ser 126,563, March 221971 tween them by the coatmg, and the wires and plastic coatingcomprise a unitary assembly defining a cylin- U-S. Cl. d ica] arc Theseat and back assemblies are each se- [5 Int. Cl. ufgd to frame portionsacross a space that flat. Field of Search 297/239, 445, 450, 452, tenstheir arcs to flatter arcs and places these assem- 297/454 458; 160/403404; 5/ 354; blies in tension along their flatter cylindrical arcs, the2 a. c... 9 17/ 21511 112, 2 seat are being convex upwardly, and theback are 267/107-51 being convex rearwardly. When a plurality of thesechairs is stacked, each seat nests over the seat of the References Citedchair below, and the backs nest too with part of the UNITED STATESPATENTS lower surface of each seat lying within the chord 2,731,0761/1956 Rowland 297/452 x across the Seat of the chair above and P of the2,s03,293 8/1957 Rowland 297/445 x a d rface f each back lying withinthe chord 3,404,916 10/1968 Rowland 297/239 across the back of the chairbelow. 3,708,202 1/1973 V V V V Primary ExaminerBobby R. Gay

Assistant Examiner-William E. Lyddane Attorney, Agent, or FirmOwen,Wickersham & Erickson Barecki et al 297/335 X 15 Claims, 16 DrawingFigures 'PATENTEUNOY 519M 3.845386 sum 2w 4 II/II/Il/IIIII/I/lll/I/II/II 1/11 I 0,, llllli m (Ill l-;qllllllllllll 1114 I-i'lllllllllli VIII; a!!! FEM STACKABLE SEATING UNITS CROSS-REFERENCE TORELATED APPLICATIONS This application is a continuation-in-part ofapplication Ser. No. 268,870, filed July 3, i972, which was a divisionof application Ser. No. l26,808, filed Mar. 22, l97l, now U.S. Pat. No.3,720,568.

This application is also a continuation-in-part of application Ser. No.268,907, filed July 3, 1972, which was a division of application Ser.No. 126,563, filed Mar. 22, 1971.

BACKGROUND OF THE lNVENTlON pactness in stacking. The non-resilientstacking chairs may be compactly stackable, with seats and backs thinnerthan the frame, but they lack the comfort-giving feature of springresilience.

Thus, the present invention is characterized by spring-resilient seatsand backs that are truly thin-- -thinner than the frame.

The term, spring resilience, is here used to distinguish the presentseat from canvas sling seats and backs and the like.

A hard seat can, at best, only approximate a comfortable shape, sincehuman posteriors vary greatly. While seats theoretically might betailor-made for each individual, this would be costly and would requirecarrying seats to wherever they would be used. A seat whichautomatically tends to shape itself to each users posterior is a bettersolution to the problem. A seat with proper resilience in the rightplaces is thus an object of this invention.

The seated human body rests mainly on the ischial tuberosities, the twolower points of the pelvis. Additionally, it rests on the meaty andfatty flesh in a l to 2 inch radius therefrom. The reason why a flat,hard surface becomes uncomfortable quickly is that the load isconcentrated on the small area of the ischial tuberosities', and theflesh immediately covering them is compressed with great force.Spreading this load over a larger area makes a more comfortablecondition as the unit area compressive force is substantially reduced.Automatically shaping the seat surface to generally conform to thesitter helps to accomplish this. On the other hand, spreading this areaover too wide a surface, such as is the case when a seat is too soft,results in engulfing the sitter too deeply and also often results in alack of security, which comes from feeling insuffi ciently supported.One often sees automobiles in which the owner has gone to the trouble ofinstalling wooden slat accessory pads to make the seat firmer.

Dr. Bengt Akerblom. eminent Swedish authority on human posture, says inhis book Standing And Sitting Posture, published by A. B. NordiskaBokhandeln, 1948, Naturally a rather soft seat would distribute thepressure over the tuberosities better than a hollowed rigid one. Theyare, however, so small that there would be very little sense in having avery soft and resilient seat. On the contrary, such a seat might beexpected to transfer a not inconsiderable proportion of the weight on totissues which are not adapted for bearing it. The best consistency forthe seat would therefore be such that although it gave under pressure,it only gave slightly."

Proper resilience alone is not enough, either. lndependent freedom ofmovement of such as that found in a two-way stretchable material moreappropriately confomis to the human posterior shape, which itself hascompound curvature.

While certain spring and padding combinations can afford properyieldability and firmness, practically all padding materials have thefault of being good heat insulators. In a cold room, this might beacceptable temporarily, but people usually wear clothes appropriate fortemperature conditions anyway, and to sit for any length of time on aheat-insulative material becomes uncomfortable because of inhibition ofdispersion of body heat in the human posterior area. To get to a coolerspot, the person squirms. Also, anyone who, while wearing a swim suit,has tried to sit down on the seat of a convertible car that has been outin the hot sun, knows that such heat conditions of the seat can beunbearable.

Some prior art seats have been made of spaced-apart wires, but in themthe spacing has been such that too much load has been concentrated ontoo few wires, and this textural discomfort has made the use ofupholstery pads requisite for such seats.

An ideal seat, therefore, has:

1. Proper shape (including proper compound curvature).

2. Proper resilience and firmness (resilience provides shapeadaptability to each sitter).

3. Proper heat dispersion.

4. Proper surface contact area.

An object of this invention is to provide a seat for stacking chairsmore nearly approaching the ideal than has been achieved in the past.

Each seat or back of this invention comprises a series of sinuous springwires, partially held together by a thin sleevelike plastic coatingaround each of the wires, bridging the wires where they touch.

The seat and back structure may be considered as an improvement over myearlier U.S. Pat. No. 2,803,293. In that patent each of the sinuoussprings had a hook on each end which partially encircled a rigid framemember. This hooking did not positively prevent movement of the wiresrelative to the frame, nor did it hold them in proper position relativeto each other prior to their being coated with plastic. Partly becausethere was only line contact at best between the wire and the frame (andunless the chair frame size was exactly matched with the size of thehook, there would be contact at only two points), the hook tended torotate when subjected to force, as when someone sat on the chair. Evenafter the chair had been coated with plastic, this instability was suchthat when the chair was being sat upon, the wire hooks tended to walkalong the chair frame as the sitter shifted his position, therebydistorting the seat area, with the result of making the seatuncomfortable. Moreover, the chair of that patent was expensive tomanufacture because the springs had to be put on individually, carefullypositioned, and then either the entire chair had to be dipped, or atleast the upper portion of the chair, from the seat up, had to bedipped. Such dipping meant that all parts of the chair that were dippedwould be coated with plastic unless something could be put on some partsof the chair to repel the plastic. Either alternative addedsubstantially to the cost. Also, the coating dulled the appearance ofchrome metal furniture, and wood furniture was given a rather unpleasingappearance. Each chair had to be made individually, and the springsthemselves had to be put on to a full chair frame individually, so thateasy handling required by mass production was not possible. Also, greatcare had to be taken that the springs themselves were not distorted bythe spring manufacturer during his manufacture; otherwise, the springscould not be properly bridged across by the plastic.

These difficulties are overcome in the present invention, which makesmass production quite feasible. Only the seat unit or back unit isdipped, and assembly is relatively inexpensive, and its manufacture iscapable of automation and other mechanical aids.

Another disadvantage of my prior chair was that the chair seat and backwere substantially planar, and, even if they did have a slight bowing,they were installed in a generally flat at-rest shape of the spring, sothat there was little spring tension or cushioning action. In thepresent invention, it becomes possible to obtain much more tension,cushioning, and resilient support from the springs by virtue of makingthe unit as a cylindrical segment that is somewhat flattened when it isput on a chair frame, rather than making chairs from a series ofsubstantially flat springs. The tension of the wires pulling inwardly isone of the main forces retaining the assembly in place.

Another important feature of the invention is the provision of a two-waystretch, which is obtained by using plastic coatings lying within aprescribed range of Shore durometers. The springs can continue theirflexing in the usual manner without being overly limited by the coating,and also the spring assembly can flex and stretch the plastic when itbridges the wires.

Even two-way stretchability and proper wire gauge alone have been foundto be insufficient. Resistance to bounciness is an important propertywhen considering the resilience necessary for a comfortable seat and isespecially necessary in transportation seating, where up-and-down motiontends to result in harmonic vibration, for harmonic vibrations subjectthe sitter to vertical oscillations for some time after a bump has beentraversed. Bounce dampening is thus requisite, and is partlyaccomplished in the present invention by proper choice of durometer ofthe plastic coating. if the durometer is too low a value, the springsare too free and are too ready to bounce. If the durometer is too high,

. the seat is too stiff and lacks the proper two-way stretch qualitydesired. Proper choice of durometer according to the principles of thisinvention, enables the plastic to serve as a shock absorber and providesa snubbing action against bounce.

Additionally, bounce-dampening can be achieved in this invention byemploying in the assembly some wires that differ from the other wires ingauge, shape, or spring tension or temper, so that their harmonicvibration periods are different.

The amount of the seating area occupied by the metal thickness, and thethickness of the plastic coating are also important features to beconsidered, and little, if any, thought on these features is evidentfrom the prior art. For example, in the drawings for U.S. Pat. No.2,803,293, it can be shown that the metal occupies only about 14 percentof the silhouette of the area, whereas l have now found that for properresults the spring steel should occupy a minimum of 17 percent of thesilhouette of the area and, preferably, but less important, a maximum ofabout percent, with the range of about 17 percent to about 25 percentgenerally preferable. The coating should generally be about one-half asthick as the wire, in order to give bridging, proper heat dissipation,and proper stretchability, but a range from about one-fifth of the wirethickness to about equal to the wire thickness can be used. Also, thesize of the void areas between the coated wires should be no greaterthan about 75 percent of the seat area used to accommodate one adultsitter and should not be less than about 2 percent, with about 60 to 75percent being preferable.

SUMMARY OF THE INVENTION The present invention comprises a compactlystackable chair having a thin, spring-resilient seat and back.Basically, each seat or back is a cylindrical segment, later flattenedsomewhat upon installation, placing the springs in tension. Sometimes ithas a rim, which usually has straight ends, typically parallel, joinedby parallel sides which are made as circular arcs, sometimes there is norim. There is a series of sinuous spring wires, each of which isattached at its opposite ends to the rim, if there is one. The wiresextend between their ends in a circular are which, when there is a rim,is parallel to the circular arc of the parallel sides of the rim. Inmost seats and backs each of the two extreme spring wires is tangent ateach cycle to one of the rim sides, and each wire touches or closelyapproaches its adjacent sinuous spring wires at least once per cycle.

More specifically, a stacking chair of this invention includes a framehaving at least two spaced-apart rigid side frame portions, two frontlegs, two rear legs, and two spaced-apart rigid back frame portions. Theframe portions and the legs are arranged to enable compact stacking. Theframe supports both a seat assembly and a back assembly, each of whichhas a series of arcuate, continuous, sinuous wires, each wire closelyapproaching each of its immediately adjacent wires at frequentintervals. A thin sleevelike plastic coating surrounds the wires,following their sinuosity and joining them together where they closelyapproach each other, the approaches being close enough for effectivebridging between them by the coating. Thus, the wires and the plasticcoating are combined in a unitary assembly defining a cylindrical are. Afirst mounting means secures the seat assembly to the rigid side frameportions across a space that flattens its arc to a flatter arc andplaces the seat assembly in tension along the flatter cylindrical are,which is convex upwardly. Second mounting means secures the backassembly to the rigid back frame portions across a space that flattensits arc to a flatter are which is convex rearwardly. When a plurality ofthese chairs are stacked, each seat nests over the seat of the chairbelow, part of the lower surface of each lower seat lying within thechord across the seat of the upper chair; similarly, each back nestswithin the back of the chair below, part of the forward surface of eachback lying within the chord across the back of the chair below.

A thin sleevelike plastic coating surrounds both the rim wires (if theyare present) and the sinous spring wires, following the sinuous shape ofthe spring wires and bridging between and joining them at points wherethey are tangent to each other or touch each other, and also joining andbridging between the rim and some positions of the wires. This thinplastic coating, while leaving most of the area of the seat open inbetween the wires, does link the wires and the rim together into aunitary assembly, shaped as a cylindrical arc. When the unitary assemblyis installed on a frame as either a seat or a back, it is flattened outsomewhat but not fully. When used as a seat, the rise between one endand the other after flattening is between a quarter of an inch and aninch, preferably. For the back, the curvature may be somewhat greater,preferably a radius of seven to twenty inches. The plastic preferably isin the range of Shore A durometers between 45 and 90, and seems to bebest at about 75, so that the two-way stretch action previously referredto is attained.

In some forms of the invention other shapes of rims are used, and instill other forms, no rim as such is necessary, being replaced by aspecial welded subassembly.

Note that in this invention the wires cannot go straight across. Theymust undulate in order to be stretchable. Moreover, they must beconnected to each other by stretchable means. This contrasts with myearlier patent which may allow flexible joints but does not requirestretchable joints. A ISO-pound person sitting normally on a chair ofthe present invention will depress it by at least 1 inch (or at leastone-eighteenth part of seat height) and, at most by about 3 inches(about one-sixth part of seat height). As stated, the junctures arestretchable and flexible, but they are also so tough that they cannot bepulled apart under usual human sitting conditions. Putty and kneadederasers have a rubbery quality, but not the elasticity, stretchability,flexibility or resilience requisite. To get the best results in thisinvention, the area of the silhouette of the wires prior to coatingshould be at least l7 percent of the seat area, especially of a typicalarea. For sufficient bridging, heat dissipation, and surface cushioning,the coating should be at least percent of the wire diameter. If the seatwere made from springs alone, the comfort would be insufficient,particularly when used in moving vehicles. It would be too bouncy.Proper durometer and proper thickness of the coating relative to thewire thickness help to prevent this bounciness. The reason is similar tothe reason why a car'is not comfortable with metal springs alone; italso needs the rubber, air, and hydraulic fluid in the combination ofrubberpneumatic tires and hydraulic shock absorbers, before it can becomfortable.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a view in perspective of a stacking chair embodying theprinciples of the invention.

FIG. 2 is a view in perspective on an enlarged scale of a seat or backunit or sub-assembly embodying the principles of the invention, shownbefore being installed on the chair frame of FIG. 1.

FIG. 3 is a view in section taken along the line 3-3 in FIG. 1.

FIG. 4 is a view in perspective of the fastener used in FIGS. 1 and 3 tosecure the sub-assembly of FIG. 2 to the chair frame in FIG. 1.

FIG. 5 is a diagrammatic view in end elevation showing the difference inradii of the cylindrical assembly of FIG. 2 and the installed seat ofFIG. 1, which has been somewhat flattened out, thereby placing thespring wires under tension.

FIG. 6 is a fragmentary enlarged view in perspective of a corner portionof the assembly of FIG. 2, somewhat flattened out. Some portions arebroken away to show other portions that would otherwise be obscured.

FIG. 7 is a further enlarged view in section taken along the line 7-7 inFIG. 6.

FIG. 8 is a view in section taken along the line 8--8 in FIGS. 6 and 7.

FIG. 9 is a view in section taken along the line 9-9 in FIG. 7.

FIG. 10 is a view like FIG. 7 showing how the springs may be installedfrom the opposite direction in the same rim unit.

FIG. 11 is a view in front elevation of the chair of FIG. 1.

FIG. 12 is a view in side elevation of two chairs of FIG. 1 stacked. Theseat of the upper chair and the back of the lower chair are broken awayto show how the other seat and back nest.

FIG. 13 is a diagrammatic view in section taken along the line A-A inFIG. 12.

FIG. 14 is a diagrammatic view in section taken along the line 8-8 inFIG. 12.

FIG. 15 is an enlarged top plan diagrammatic view in two halvesillustrating the two-way stretch effect of the wires and plasticassembly.

FIG. 16 is a fragmentary view in perspective of a portion of a modifiedform of seat assembly of the invention installedon a stacking chair asthe seat thereof and showing a portion near a rear corner of the seat.Parts are broken away and shown in section. This view illustrates theadaptability of the invention to double curvature in the seat, asoccasioned by curvature of the supporting frame.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS An Example of a Stacking ChairEmbodying the Invention (FIG. 1)

Many, many types of seating units may embody the principles of thisinvention, including chairs, sofas, and davenports.

A stacking chair 60 is shown in FIG. 1 for the purpose of giving oneexample of a type of seating unit that can embody the principles of theinvention. This example is not to be construed as representing all typesof seating units or even all types of the chairs, which can vary greatlyin frame structure, appearance, and so on. The basic part of thisinvention is concerned with the seating and back unit and the stackingrelationship mrffre than with the specific framework of the chair itseCompactly stackable chairs such as those shown in my US. Pat. No. Re.26,071 may be used in conjunction with the present invention to providea more resilient seat than the hard seat heretofore used with thosechairs. The chair frame may have curved lines, as discussed inconnection with FIG. 16 by virtue of this invention, and the seats andbacks are easily made so that they nest within each other when the chairframes are stacked, so long as the chairs themselves are of stackablestructure. Any type of stackable structure may be used with these seatsand backs, and since they are quite thin, a compactly stackablestructure becomes feasible with the stacking height of a set of chairsbeing determined basically by the thickness of the chair frames. Thesechair frames, if desired, may be made quite thin.

FIGS. 13 and 14 show how the seats and backs stack one within the other.it will be seen that the chord across the arc of the one chairintercepts the arc of the next adjacent chair. The same basicconfiguration also applies to the seats.

The chair 60 has front legs 61, 62 and rear legs 63 and 64 which arewider apart than the front legs 61, 62

and continue up, preferably at an angle, to form back frame portions ormembers 65 and 66. The number of pieces used in making the chair frameis immaterial to this invention, and whether the frame is continuous orpieces are welded or otherwise secured together does not matter, so faras the present invention is concerned. Horizontal side frame portions ormembers 67 and 68, the same distance apart as the front legs 61, and 62,join the front legs 61 and 62 to the inner edges of the rear legs 63,64, preferably at the point where the rear legs 63, 64 meet the backframe members 65 and 66. The use of bracing members is not significantin the present invention, though a rear bracing member 69 that iscontinuous with the members 67 and 68 and a front bracing member 69a areshown in the drawing, and there must be some rigid means for holding theframe members 67 and 68 apart and for holding the frame members 65 and66 apart. in this particular form of the invention the back framemembers 65 and 66 are rigidly held parallel to each other and the sideframe members 67 and 68 are rigidly held parallel to each other. Thisparallelism need not always be present, but it is preferred, as is oneway of assuring stackability in the structure shown. In any event, thechairs should be stackable as compactly as the frame members themselveswill permit.

A seat unit 70 is supported by the side frame members 67 and 68 and aback unit 70A is supported by the frame members 65 and 66. The seat unit70 and the back unit 70A are very similar to each other; they may insome instances be identical, but usually the back unit 70A is somewhatsmaller than the seat unit 70 and is usually made from a smaller gaugeof wire.

The structure of the units 70 and 70A is highly important in thisinvention. So is the attachment of the units 70 and 70A to a chairframe.

The Seat Unit 70 (FIG. 2)

FIG. 2 shows the seat unit 70 before it is incorporated into the chair;the view also represents basically what the unit 70A looks like,although the unit 70A may be different in size or even in structure orappearance, where desired.

in this example the unit 70 comprises a rim 7! having spaced-apartstraight ends 72 and 73 joined by parallel side members 74 and 75, whichare shaped as circular arcs. The member 74, which is to extend acrossthe front edge of the seat, may be of thinner gauge than the wires 76,etc., in the remainder of the seat. Lest there be some confusion in themind of the reader, it is pointed out that the straight end members 72and 73 are secured to the side frame members 67 and 68 of the chair, andthus extend from front to rear at each side of the chair 60, while theside members 74 and 75 become the front and back edges of the seat inthe assembled chair 60. However, so far as the seat unit 70 itself isconcerned, the members 72 and 73 are the ends and the side members 74and 75 are arcuate or circular sides. As shown in FIG. 16, there need beno rim 7] or members 72 or 73.

Extending from end to end across the two end members 72 and 73 is aplurality of sinuous spring wires 76, 76a, 76b 76n, which are naturallyarched into a circular arc of the same size and shape as that of theside members 74 and 75. These springs 76, 760, etc., may have manyshapes, some of which are shown in the parent application. They may beof the type often called non-sagging springs and sometimes sold underthe trademark No-Sag. Typical wires 76, etc., of this type are of springsteel, having 0.60 to 0.75 percent carbon and 0.90 to 1.20 percentmanganese. Tensile strength typically runs about 215,000 to 265,000p.s.i., and their Rockwell hardness is about 39-41 RC range. Thediameter of the wires 76, etc., preferably lies in the range of 0.05inch to 0.l5 inch. Too thick a wire tends to concentrate the stiffnesstoo much and the seat is too firm, while too thin a wire makes the seattoo soft. Some of the wires 76, etc., may be thinner than others,especially toward the front of the seat. Some of the wires may havedifferent vibration frequencies than others, some may be thicker to snubvibration. Some wires may be of different arc-cycle length than others,or some may be of different temper from others, to accomplish thispurpose of snubbing vibrations.

Each end 77, 78 of each spring (See FIGS. 6-10) is firmly anchored toand secured to one of the end members 72, 73 of the rim 7]. Variousmeans are employed to achieve this firm anchorage, and some of these aredescribed below in following sections. They include friction grips andwelding, among the many types of mechanical connections.

The spring members 76, 76a, 76b, 76n are placed tangent to each other,each of the two extreme spring wires 76 and 76n being substantiallytangent at each cycle to one of the side members 74 and 75. Each wire 76touches its adjacent wires at least once per cycle. The touching may beactual contact or it may be approximate touching or close approach,because, as will be seen, the assembly 70 is held together in a way thatdoes not require actual physical contact of the metal at each tangentpoint, but it is always a very close relationship if not an actualtouching.

A thin sleevelike plastic coating 79 surrounds the spring wires 76,follows their sinuous shape, and bridges the wires 76, 76a, etc., wherethey substantially touch each other. Preferably, the plastic coating 79is about one-half of the wire thickness, or in the range of aboutone-fifth of the wire thickness to about equal to the wire thickness. Atthe junctures, the thickness may be mostly greater, though the wiresthemselves may touch each other. This plastic coating 79 also surroundsthe rim 71 and links the wires 76 and the end and side members of therim 71 together into the unitary assembly 70. The plastic coating 79holds the wires 76 to each other as they span between the rim ends 72and 73, and it holds the side wires 74 and 75 to the extreme springs 76and 76n at each point of tangency. The result is the arcuate orcylindrical arc shape, typically like that shown in FIG. 2, although thearc may be somewhat flatter or somewhat rounder Thus, the completeassembly 70 is a unit which can be sold or shipped as a unit and can beassembled to the chair 60 of FIG. 1 or to many other kinds of chairs, solong as the proper size and shape is accommodated for in one way oranother, that is, either by the chair itself being shaped to go with theseat unit 70 or the seat unit 70 itself made so that it will go with achair frame or other type of seating unit frame. The unit 70 by itselfis capable of mass production, and is easily assembled into a chair orother seating unit by securing the two end members 72 and 73 to asuitable rigid frame.

An Independent Type of Securing Means (FIGS. 3 and Various securingmeans may be used, as described in the parent applications. Basically,the securing means may be an integral part of the unit 70, or may be anintegral part of the chair frame or other frame to which the unit 70 isto be secured, or it may be an independent member not an integral partof either of these. An example of the last-mentioned type is thesecuring member 80 shown in FIGS. 3 and 4. This may be a suitable metalor plastic member having a generally tubular rim-receiving portion 81,with an opening 82 therethrough that fits snugly around a rim member 72or 73. The member 80 has a pair of flanges 83, 84 having an opening 85through them. As shown in FIG. 3, the chair frame member 67 may have aseries of openings 86.

adapted to receive the two wings 83 and 84, after the member 80 has beenfastened around the rim member 72 or 73. Then a suitable screw 87 may beinserted through a suitable opening 88 of the frame member 67 andsecured by means of the openings 85 to the wings 83 and 84. As shown inFIG. 1, there may be several of these units 80 to secure the seat unit70 and the back unit 70A to the chair 60.

From this it will be apparent that the assembly 70 and the assembly 70Amay be made as units by one manufacturer and sold to anothermanufacturer who makes the chair frames. So long as the dimensioning iscorrect, the two manufacturers need not know precisely what each otheris doing, for the unit 70, if made in the correct dimensions, can besecured to a variety of different types of chair frames, or to otherframes of seating members, for that matter, including benches,automobile frames, and so on. The unit 70 enables the chair manufacturerto secure the seat or back in place in the most attractive and pleasingand most practical way.

As will be seen from later portions of the specification, there aremany, many ways in which the fastening of the member 70 to the chair 60can be done, and this is just one example. The Significance ofFlattening the Cylindrical Arc (FIG. 5)

FIG. 5 shows diagrammatically what happens when the unit 70 of FIG. 2 isput into the chair 60 of FIG. I. The round cylindrical arc of FIG. 2with radius R1 is flattened from the shape shown at the bottom of FIG. 5to the shape shown at the top of FIG. 5, where it has a larger radiusR2. The unit 70 then has a broader span and its arc is somewhatflattened. so that it can be used as a seat. It has a crown height h,shown on the drawing, and it is still a cylindrical arc, though muchflatter.

This flattening of a round assembly is an important feature of theinvention. By forming the unit 70 initially as a cylindrical arc, whichis quite round and fairly well closed, and then flattening itconsiderably, a large amount of desirable tension is placed into thecompleted unit 70, so that the seat has a springy feel to it, actingsubstantially as though there was a large cushion instead of simply anassembly of thin springs. The exact amount of crown height h or ofcurvature depends, of course, somewhat on taste, but generally therewill be about a maximum of one-inch crown height h in a sixteen-inchwide seating unit 70, and the proportion is usually best considered asbeing. a crown height h of one-sixty-fourth to one-sixteenth of thespan.

The amount of force required to flatten a seat of typical dining chairsize is important as well. For purposes of the present invention it hasbeen found that a collection of springs in an assembly 70, requiring aforce of between 340 pounds and 680 pounds to flatten it gives a seat ofproper tension, (preferably around 500 pounds). This is the forceexerted in pulling the two ends 72, 73 apart to be of an appropriatedistance to fit onto the chair frame members 67, 68.

For the chair back, somewhat different rules apply and it will benoticed that in the chair of FIG. 1, as in most such chairs, the arc ofthe back extends rearwardly and is not something that the sitter tendsto flatten; rather, he tends to increase the arc curvature, reducing itsradius.

In both the seat and the back, the tension of the wires pullinginwardly, which results from flattening, is also one of the main forcesretaining the wires in place. Significance of the Plastic Coating 79(FIG. 15)

The plastic coating 79 may be chosen from various types of plastic, suchas polyvinyl chloride, polyvinyl acetate mixtures thereof, other vinylcompounds, polyethylene, butadiene, acrylic elastomers, and so on. Thematerial may be transparent, where that is desired, or may be opaque andimpart its own color to the unit. It may contain dye or pigment whichimparts a desired color, completely preventing view of the wires 76themselves and giving the appearance of constituting the actual seatingmaterial. The plastic coating 79 may be semi-transparent and may giveshade or tone to the overall color.

It will be noticed that in this invention the plastic is confined to theunit or 70A and is not applied at all to the chair frame, so that thechair frame may have any surface or treatment that is desired withoutinterference from the nature of the plastic coating.

The sinuous wires 76 are preferably not welded to each other at theirpoints of tangency but are held together only by the plastic coating 79,with the wires 76 either touching each other or even slightly apart butclosely approaching each other. The same is true of the connectionbetween the wires 76 and the arcuate side members 74 and 75 of the rim71.

An important feature of the plastic coating 79 is that by choosing theproper range of durometer, a two-way stretch effect can be obtained, asillustrated in FIG. 15. The springs 76 not only stretch in the wellknown manner of non-sagging springs, but also the plastic coating 79between the adjacent springs 76 may be stretched, and this two-waystretch effect gives a wide range of resilience to the seat. If theplastic 79 is too hard, there can be substantially no such stretch, andif the plastic 79 is too soft, there will be too much stretch, thesprings 76 themselves are not properly availed of, and

the unit 70 might even be torn apart after short use. By

holding the Shore durometer of the plastic coating within criticalvalues, the effect is right, with sufficient rigidity so that thesprings 76 are taken advantage of and so that they are held apart withsufficient resilience so that the whole is not simply encased in a rigidcovering. I have found that the durometer range necessary to achievethis critical action is from about 45 to about 90 Shore A-scaledurometer, with a preferable value of about 75.

In FIG. there are two portions. The left portion illustrates part of aseat 70 before it is sat upon, with the springs 76 therefore in theirnormal configuration. A typical area 280 is shown outlined, this areacomprising one complete cycle of wires 76, so that it is representativeof the total area of the seat 70 so far as the percentage of metalsilhouette per total area is concerned. This area can therefore be usedfor determining accurately the silhouette of the wire and its averageoccupation of the seat area. Taking the gauge or wire diameter as G, thelength of the wire can be determined in terms of G by measuring thelength of the center lines of all the wires 76 in the area 280 in termsof G, and the value is found to be 340. The area 280 itself measures14.60 by 10.70, which is 156.220 The silhouette area of the wire in thearea 280 is 340 which is 21.76 percent of the area 280. This value lieswithin the required range of l7 to about 75 percent of the seat area,mentioned earlier, and also within the range of the preferred range of17 to about 25 percent.

Also, the empty spaces between the coated wires should be no greaterthan about 75 percent and no less than about 2 percent of the area ofthe seat surface, and the range of about 60 to about 75 percent ispreferred. The minimum of about 2 percent barely provides sufficient airventilation.

The wires 76 in the seat 70 lie closely adjacent each other and nearlytouch at points of near-tangency, where the distance D] between them, asshown in FIG. 39, may be as low as zero, and where the overall distancefrom the outside to the outside is TI. The plastic coating 79 forms abridge fastening the wires 76 together at 281 and has a thickness t.

The right portion of FIG. 15 illustrates what happens when the seat 70is stretched, as when it is sat upon. The length L1 in the left portionextends to the longer length L2 in the right portion. The width Wl inthe left portion extends also to become the width W2 in the rightportion. The distance D1 in the left portion has stretched to become thedistance D2 in the right portion, and the distance T1 has stretched tobecome the distance T2. Thus is seen the importance of the bridge orjuncture 281 and of the stretchability of the plastic 79 at this bridgeor juncture 281. This, of course, is related also to the thickness t ofthe plastic coating 79.

A glance at the seat 70 might lead one to conclude that the surfaceconfiguration would be texturally uncomfortable. However, thisconclusion would be mistaken, for the seat 70 acts differently than onemight at first conclude, for the following reasons:

1. The average occupation by the wire of the typical area (Le, 17 to 75percent) is so great that the human posterior is supported withoutconcentrating the load too much. In contrast, if the wire occupies lessthan about 17 percent of the area (e.g., the 14.4 percent occupation ofthe FIG. 2 area in US. Pat. No. 2,803,293), the seat would be texturallyuncomfortable.

2. The empty spaces constitute at least 2 percent of the seat area, inorder to give sufficient air ventilation, and preferably occupy muchmore of the seat area, up to about 75 percent.

3. The wire 76 is not exposed bare metal, which would be highly heatconductive and therefore unpleasant and uncomfortable. The wire 76 isadequately coated with plastic 79 which is low in heat conductivity; soit is pleasant and comfortable to sit upon.

4. The coating 79 lies within the range of Shore A durometers (45-90)where it is neither too hard nor too soft; in fact it tends in itself toprovide some cushioning effect, and its action at the bridges 281 addsto the comfort. Without this, the seat could be too hard or too soft.

5. The two-way stretch discussed above provides automatic contouring,offering minimal resistance to the human posterior. Without this two-waystretch, the seat 70 might become increasingly uncomfortable.

Friction Fastening of the Wires to the Rim (FIGS. 6-10) While many meansof fastening the spring 76 to the rim 71 may be employed, some arenaturally preferred above others. The preference depends on manyfactors, such as manufacturers capabilities and preferments,specifications given by customers, and various features of cost andcapital equipment required.

One desirable type of fastening employs afriction lock principle, shownin FIGS. 6-10. In this form, the rim 71 has end members 72 and 73 thatare generally tubular; they may be made as a solid tube, but,preferably, as shown in the drawings, each member 72 or 73 is an opentube that may be made by curling a narrow strip of metal in a generallycircular shape. As shown, the member 72 or 73 has a flat bottom portion90 which is punched through at intervals to provide openings 91 andwings 92 and 93, extending at an angle such as about 30. Machines formaking these on either a batch basis or on a substantially continuousbasis are readily devised, so that the members 72 and 73 may be made aslong strips cut into desired lengths.

As will be seen by comparing FIGS. 7 and 10, the member 73 may beconsidered as being the same as the member 72, so that they arereversible; in other words, the same piece may be used in eitherdirection and at either end of the rim. Of course, bending in onedirection in reversal is a possibility, but no such reversal or sense ofdirection is required when the wings 92 and 93 are made as shown.

A series of side openings or slots 94 provide an entryway for the wireend 77 or 78. The wire end 77 or 78 is inserted in the opening 94 andthen moved lengthwise of the member 72 or 73 until it is stopped byengaging one of the wings 92 or 93. When inserted, the wire 76 depressesthe wing 92 (or 93) under pressure, but when it engages the end of thefar wing 93 (or 92), it can progress no farther. Thus, accuratepositioning is assured, and this can be made to provide automaticallythe desired tangencies of the wires 76 with each other and with the sidemembers 74 and 75 of the rim 71. Once inserted, the wire end 77 or 78cannot be retracted, because on retraction, the depressed wing 92 (or93) digs into the wire 76 and prevents outward movement. The intentionis to prevent any relative movement between the wire end 77 or 78 andthe member 72 or 73 after assembly. The wire 76 can move across adepressed wing 92 in the direction toward a stop wing 93 but cannot moveback against the wing 92, once it has been moved in. As shown in FIGS. 7and 10, the movement can be in either direction with the same effectexactly; it may be, of course, in opposite directions at opposite endsof the rim 71. Thus, the wires 76 are locked into the complete assemblyby friction in this form of the invention. The plastic coating 79 isapplied after this assembly is completed.

Friction Fastening of the Wires to the Rim (FIG. 16)

Many means of fastening the spring ends 77 and 78 to a frame member maybe employed. Some of them are illustrated in the drawings in order togive some idea of the wide variations that are possible under thisinvention, but of course there are many others that could not be shownwithout the specification becoming too long.

In FIG. 16, a frame member 100 is provided with a securing member 101which is a cylindrical segment, as seen in cross section, and has a mainbody portion 102 that may be welded to the frame member 100, a similarone being welded to the opposite frame member, not shown here. A seriesof projecting tongues 103 are provided, which may be initially made in abent-up'position and then bent down into place as shown in FIG. 16,after the wire ends 77 or 78 have been approximately positioned so as tolock the wire ends 77 or 78 into place firmly by the members 103,clamping them between the members 103 and the frame 100. As shown inFIG. 16, this may extend along a curve, or it may extend along astraight line. Both are equally possible in the present invention, andthis is a very important and unique effect of the present invention. Itwill be seen that with the members 101 welded on the frame members 100,installation is a relatively simple matter, involving principallyflattening out and stretching the arc of the subassembly 70, anchoringone end of it first and then anchoring the other end. The plastic 79 maycover the ends 77 and 78 or may not, but installation is the same inthis instance in both forms. Preferably, a plastic bearing block liesbelow each tongue 103. This bearing block is preferably made fromplastic that is stiffer in consistency than the coating 79, and itserves as a cushion preventing the tongues 103 from abrading or cuttingthrough the coating 79.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

I claim:

1. A stacking chair, including in combination:

a. a frame having at least two spaced-apart rigid side frame portions,two front legs, two rear legs, and two spacedapart rigid back frameportions, said front legs and said rear legs being spaced apart atdifferent distances and being operatively connected with theirrespective frame portions to enable compact stacking,

b. a seat assembly and a back assembly, each having a series of arcuate,continuous, sinuous wires, each having two ends, each said wire closelyapproaching each of its immediately adjacent said wires at frequentintervals, and a thin sleevelike stretchable plastic coating surroundingsaid wires, following the sinuosity of said wires and joining said wirestogether where they closely approach each other, said approaches beingclose enough for effective bridging between them by said coating,whereby said wires and plastic coating comprise a unitary assemblydefining a cylindrical are,

c. first mounting means for securing said seat assembly to said rigidside frame portions across a space that flattens said arc to a flatterarc and places said seat assembly in tension along the flattercylindrical arc, which is convex upwardly, and

d. second mounting means for securing said back assembly to said rigidback frame portions across a space that flattens said arc to a flatterarc which is convex rearwardly, each said seat assembly, when aplurality of said chairs are stacked, nesting over said seat assembly ofthe chair below, with part of the lower surface of each lower seatassembly lying within the chord across the seat assembly of said chairim mediately above, the back assemblies being similarly nested.

2. The stacking chair of claim 1 wherein each said assembly includes:

a rim defining a closed area of a cylindrical surface arched in onedirection and straight in another direction normal to said archeddirection, and having springy flexing action along said archeddirection,

said series of sinuous wires each being positively anchored at oppositeends to said rim and extending across said rim in a generally circularare parallel to the arching of said rim, the longitudinal axes of saidwires being parallel to each other,

said thin sleevelike plastic coating surrounding said rim, linking saidwires to said rim in a unitary assembly shaped as a cylindrical archaving a curvature of less radius than that desired in said seat orback.

3. The stacking chair of claim 2 having means for mounting said rim onsaid frame members, and for flattening said wires somewhat to place thewires in tension along said flatter cylindrical are.

4. The stacking chair of claim 1 having mounting means for securing,separate from said coating, each said assembly to its said rigid frameportions, thereby preventing relative sliding movement of said wirestherealong, said frame portions being so spaced apart that installationflattens said are to a flatter arc and places the assembly in tension.

5. The stacking chair of claim 4 wherein said mounting means comprisesmeans for anchoring each of said wires adjacent their ends, the tensionunder which the wires are placed helping to retain them in place.

6. The stacking chair of claim 5 wherein each said mounting'meansengages the actual wire ends to prevent movement of the two ends of eachsaid wire toward each other.

7. The stacking chair of claim 4 wherein said wire ends lie in the sameare as the remainder of their wire.

8. The stacking chair of claim 7 wherein said mounting means comprises amember having transversely outwardly extending tongues to which saidwire ends are engaged, said tongues being bent down over said wires.

9. The stacking chair of claim 8 wherein said mounting means is anintegral portion of said frame, said tongues being bent out portions ofsaid frame.

10. The stacking chair of claim 1 wherein said frame is curved and saidassembly is attached to the frame curve and is imparted a compoundcurvature.

11. The stacking chair of claim 1 wherein the wires in the seat lyingclosest to the forward edge of the chair are of lighter gauge than thewires of the seat in the central portion thereof, thereby impartingincreased comfort.

afford the bounce dampening.

1. A stacking chair, including in combination: a. a frame having atleast two spaced-apart rigid side frame portions, two front legs, tworear legs, and two spaced-apart rigid back frame portions, said frontlegs and said rear legs being spaced apart at different distances andbeing operatively connected with their respective frame portions toenable compact stacking, b. a seat assembly and a back assembly, eachhaving a series of arcuate, continuous, sinuous wires, each having twoends, each said wire closely approaching each of its immediatelyadjacent said wires at frequent intervals, and a thin sleevelikestretchable plastic coating surrounding said wires, following thesinuosity of said wires and joining said wires together where theyclosely approach each other, said approaches being close enough foreffective bridging between them by said coating, whereby said wires andplastic coating comprise a unitary assembly defining a cylindrical arc,c. first mounting means for securing said seat assembly to said rigidside frame portions across a space that flattens said arc to a flatterarc and places said seat assembly in tension along the flattercylindrical arc, which is convex upwardly, and d. second mounting meansfor securing said back assembly to said rigid back frame portions acrossa space that flattens said arc to a flatter arc which is convexrearwardly, each said seat assembly, when a plurality of said chairs arestacked, nesting over said seat assembly of the chair below, with partof the lower surface of each lower seat assembly lying within the chordacross the seat assembly of said chair immediately above, the backassemblieS being similarly nested.
 2. The stacking chair of claim 1wherein each said assembly includes: a rim defining a closed area of acylindrical surface arched in one direction and straight in anotherdirection normal to said arched direction, and having springy flexingaction along said arched direction, said series of sinuous wires eachbeing positively anchored at opposite ends to said rim and extendingacross said rim in a generally circular arc parallel to the arching ofsaid rim, the longitudinal axes of said wires being parallel to eachother, said thin sleevelike plastic coating surrounding said rim,linking said wires to said rim in a unitary assembly shaped as acylindrical arc having a curvature of less radius than that desired insaid seat or back.
 3. The stacking chair of claim 2 having means formounting said rim on said frame members, and for flattening said wiressomewhat to place the wires in tension along said flatter cylindricalarc.
 4. The stacking chair of claim 1 having mounting means forsecuring, separate from said coating, each said assembly to its saidrigid frame portions, thereby preventing relative sliding movement ofsaid wires therealong, said frame portions being so spaced apart thatinstallation flattens said arc to a flatter arc and places the assemblyin tension.
 5. The stacking chair of claim 4 wherein said mounting meanscomprises means for anchoring each of said wires adjacent their ends,the tension under which the wires are placed helping to retain them inplace.
 6. The stacking chair of claim 5 wherein each said mounting meansengages the actual wire ends to prevent movement of the two ends of eachsaid wire toward each other.
 7. The stacking chair of claim 4 whereinsaid wire ends lie in the same arc as the remainder of their wire. 8.The stacking chair of claim 7 wherein said mounting means comprises amember having transversely outwardly extending tongues to which saidwire ends are engaged, said tongues being bent down over said wires. 9.The stacking chair of claim 8 wherein said mounting means is an integralportion of said frame, said tongues being bent out portions of saidframe.
 10. The stacking chair of claim 1 wherein said frame is curvedand said assembly is attached to the frame curve and is imparted acompound curvature.
 11. The stacking chair of claim 1 wherein the wiresin the seat lying closest to the forward edge of the chair are oflighter gauge than the wires of the seat in the central portion thereof,thereby imparting increased comfort.
 12. The stacking chair of claim 1wherein some of said wires have a different vibration frequency fromother wires, in order to dampen bounce.
 13. The stacking chair of claim12 wherein some of the wires are of different thickness than others, toafford the bounce dampening to said assembly.
 14. The stacking chair ofclaim 12 wherein some of the wires are of different configuration andarc-cycle length than others, to afford the bounce dampening.
 15. Thestacking chair of claim 12 wherein some of the wires are of differentspring temper from others, to afford the bounce dampening.